South Dakota Department of Transportation
Project Synopsis
SD1995-15

Problem Statement:In 1991, "The Effects of Increased Truck Tire Loads on Pavement" (SD92-06) was selected by the Research Review Board for a research study. The research was completed in November of 1993 by Huntingdon/Austin Research Engineers, Inc. That studys field observations indicated:

An increasing number of truck owners are replacing dual tired wheel configurations with super single tires or singled-out-dual tires,

A growing number of truck owners are installing lift and/or tag axles equipped with minimum sized single tires to carry legal loads.

More load is carried on each tire and these tire loads are approaching the legal maximum, 600 pounds per inch width of tire.

The damage caused by super singles is 2.2 times that of the conventional dual tire configuration and for singled-out duals it is 2.7 times that of the conventional dual tire configuration.

The tire load level is nearly double the pounds per inch width of tire load caused by a typical, conventional dual tired wheel configuration. The study defined increased tire load as carrying the same load on less tire width in configurations such as super singles, singled-out duals and lift and/or tag axles.

One of the studys key recommendations was that a more complete survey should be conducted to determine the extent and time distribution of truck tire configurations in use throughout South Dakota. Information is needed on the numbers of these types of configurations to provide data that can be used to justify legislation to change the legal maximum of 600 pounds per inch width of tire to 500 pounds per inch width of tire. The data collected should show that additional damage done by these tire configurations is detrimental to the States pavements.